Under hypertext transfer protocol (HTTP) specifications, when a server receives a request associated with a resource, the server may provide a Last-Modified header to the client device. The Last-Modified header may include an update time of the resource having a maximum granularity of whole seconds. For example, the update time may be 2 seconds or 3 seconds but may not be 2.5 seconds since sub-seconds is beyond the maximum granularity of the Last-Modified header. As a result, when a resource stored at a server is updated more than once within the same second, for each update after the first update in that second, the server may not accurately respond to validation requests from the client device when the validation requests include an update time of the first update. For example, the server may inaccurately indicate that the client device has an up-to-date copy of the resource when, in actuality, the client device does not have an up-to-date copy of the resource. Accordingly, the client device may never receive updates to a resource that occur after a first update to the resource that occurs within the same second.
There will be an ever-present need for improved techniques for ensuring the validity and currency of resources and accurately responding to requests from a client device for the resources.